The reason Mr Romney pays a lower rate than say President Obama (26%) or Newt Gingrich (over 30%) is because there's a different tax rate for income and investments.

That raises a much wider argument, and one that will be central to the election in November. It is precisely why the billionaire investor Warren Buffet said the tax rate was unfair and should be changed because he paid a smaller proportion of his income than his secretary.

Mr Obama has taken up that call with enthusiasm, even naming his proposed rule after Mr Buffet.

It plays in to a national debate on wealth and fairness that could be critical to Mr Obama's re-election or defeat. The president will make the idea of a fairer society, where the rich do more to help the struggling middle classes, a centrepiece of his state of the union speech tonight.

On Monday, before he released his income and tax figures, Mr Romney defended his tax record at a Republican presidential debate in Florida.

"I pay all the taxes that are legally required and not a dollar more. I don't think you want someone as the candidate for president who pays more taxes than he owes," Mr Romney said.

On Tuesday, Mr Romney's campaign released his 2010 tax papers and estimates for his 2011 taxes, for which he has not yet filed a return.

He and his wife Ann reported income of $21.6m in 2010 and $20.9m last year, almost all it from investments. There were no declared wages on the 2011 estimate.

They gave $7m to charity in the same period, about half of it to the Mormon Church.

President Barack Obama and his wife Michelle released their 2010 tax return in April last year, showing an income of $1.7m. They paid about $450,000 in federal tax, a rate of about 26%.

Tax debate

Mr Romney had promised to release the figures, saying the question of tax had become a distraction for his campaign, and he wanted to re-focus on the main issues.

However, he had initially refused to release the returns, saying the financial disclosure reports that all federal candidates must provide should be enough.

But the reluctance allowed his Republican rivals and Democratic critics to focus on his record at private equity firm Bain capital, painting him as a wealthy businessman who cut jobs and shut down firms.

Mr Romney's supporters have leapt to his defence, equating attacks on his business practices with criticism of American capitalism itself.

Media reaction

For the Washington Post, the storm that blew up over Mitt Romney's tax returns is a spectacular example of campaign mismanagement, fraught with "political danger" write Chris Cilizza and Aaron Blake.

That storm is not over yet, many commentators predict. "There are certain to be more nuggets of interest revealed - like the fact that he had a Swiss bank account that was closed in 2010," says Dashiell Bennett in the Atlantic Wire.

And that continuing debate does not bode well for Romney, Paul Blumenthal in the Huffington Post agrees. "It isn't as though Romney is the first very wealthy man to run for president, but he has a way of highlighting his wealth in a way that brings to mind the famous quip by the former Texas Gov Ann Richards about President George HW Bush: 'He was born with a silver foot in his mouth.'"

For Bloomberg's David J Lynch and Steven Sloan, the issue has ignited a debate over the fairness of "so-called carried interest provision, which provides a relative handful of investment executives with preferential tax rates".

They expect the Democrats to seize on the issue, perhaps as soon as President Obama's State of the Union address on Tuesday, which is expected to revolve around a theme of "economic fairness".

Mr Gingrich, who polled poorly in both Iowa and New Hampshire, won a convincing victory over Mr Romney in South Carolina after attacking Mr Romney over his business and tax records.

Mr Romney has called on Mr Gingrich to release documents related to his involvement with mortgage giant Freddie Mac.

In latest debate, Mr Romney said Mr Gingrich was doing business with Washington's "chief lobbyists".

Mr Gingrich said he served as a historian and consultant for the company, not a lobbyist.

Earlier on Monday, Mr Gingrich released his 2006 contract with Freddie Mac, but the document did not cover most of his multiple-year working relationship with the company.

The candidates are now campaigning in Florida, which holds its primary on 31 January. The state is seen as a major battleground in the US general election, with a diverse electorate and and a cash-hungry advertising market.

Primaries and caucuses will be held in every US state over the next few months to pick a Republican nominee to take on Democratic President Barack Obama in November.

The eventual winner will be anointed at the party convention in August.

Comment number 263.

lostalex24th January 2012 - 16:18

"You americans can talk all you want, this site is paid for with british 'tax-payers' money.Yes that is right we have to pay for this."

WRIONG, i'm An American, and there are ads on this website, the BBC is making money from American's viewing this qwebsite, so Amerivan's have just as much right to comment! get it right. You're tac payer money is not what keeps the BBC afloat, BBc is comerical

Comment number 261.

swenk2224th January 2012 - 16:16

Do YOU KNOW that all the money that Romney had invested in these corporations has ALL READY been taxed at full rate. Now he is gaining return on his investment and these cap gains are taxed at 15%. The engine of the economy- investment of your all ready taxed $ in business is encouraged.

Comment number 258.

beammeup24th January 2012 - 16:09

This is just the Press. As far as I know, no one in Congress/Senate or running for President is....poor.

Good thought for the rest of us "they have more to lose than we do financially." Bad thought, voters get to choose a Republican, election is held, someone wins and for them...its business as usual. For us we wait another 4 years (well 2 actually) and it begins again.

Comment number 253.

petrohwk24th January 2012 - 15:57

Slow down for a second, most americans pay less than 15% tax (I think the average is just above 11%), and Romney's 14-15% is capital gains tax, not earned income tax.

Also under Gingrich's tax plan Romney would pay 0% tax on capital gains. And can I just mention that Romeny also pays 10% to his church, which also happen to have the world's largest and most effective humanitarian aid program

Comment number 252.

Whenknew24th January 2012 - 15:57

224.Pyrogenic

How about you start with tellling us where the banking crysis started.

Second also tell us how many lies YOUR previous government told about Iraq and how much our previous government went along with that.As for aid we seem to give aid to nations with dictators/corrupt governments which then purchase our weapons.Then all they do is skim off the profits as investors simple greed.

Comment number 251.

RodgerJohnComment number 251 is an Editors' Pick24th January 2012 - 15:51

I have no problem with anyone legally reducing their tax rate from 35% to 15% with a 7 million dollar donation to charity! Go Romney! In fact this gives me greater admiration for a candidate I barely knew. Taxpayers who contribute to charities are rewarded with lower effective tax-rates as they give more. Add Romney's charitable contributions and taxes paid and his "real tax-rate" is MUCH higher!

Comment number 250.

SpectateSwamp24th January 2012 - 15:52

Question the Questioner: How do they get the privilege to ask the questions that determine who gets voted for? These aren't the questions the citizens would ask. Boo Chamber of Commerce, Big Business and Old Media.

Comment number 248.

RedRebel5424th January 2012 - 15:49

You keep believing your right wing myths then IAbide. I prefer to believe all the money went into hedge funds and thus COST jobs rather than created them. You have no more proof of your theory than I have of mine, so each to their own eh?

Comment number 247.

teedoff24th January 2012 - 15:49

@238.farkyss

Nail on the head. The "good old days" of close-knit communities were a direct result of need. You looked after everyone so they would look after you when you needed it. Today's UK has a Gov't to look after them - whatever they do or don't do - so community is gone. US still has community.

Comment number 246.

IAbideByTheTruth24th January 2012 - 15:46

@RedRebel54If you have $1billion and never invested it, you get $0 return. But if you invest $250 million, that money is used to hire people to work it. Those people, can't tell how many, must have worked hard enough for you to get $42 million return out of that investment. Its a simple business rule, investments creates jobs. No jobs will be created if people put their money in a safe.

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